This invention relates to controlling residential forced air HVAC systems, specifically an improved zone climate control system, for installation in an existing HVAC system, that is less expensive, easier to install, and provides more utility than the prior art, such that a plurality of rooms in the residence each have independent temperature regulation according to predetermined temperature schedules and locally entered temperature commands, and such that the air in each room is heated or cooled according to the occupancy and the activity in said room, improving the comfort of the occupants and reducing the energy used to heat or cool the residence.
The majority of single-family houses in the United States have forced air central heating systems. Many of these also have air conditioners that use the same air distribution system. These heating, ventilation, and air conditioning (HVAC) systems are typically controlled by a single, centrally located thermostat. The thermostat controls the HVAC equipment to maintain a constant temperature at the thermometer. The temperatures in other rooms of the house are not actively controlled, so the temperatures in different rooms can differ by many degrees from the temperature at the thermostat.
Manually adjusting the airflow to each room is the primary method available to control the temperature away from the thermostat. However, the temperatures away from the thermostat depend on many dynamic factors such as the season (heating or cooling), the outside temperature, radiation heating and cooling through windows, and the activities of people and equipment in the rooms. The desired temperature also depends on the activity of the occupant, for example lower temperatures for sleeping and higher temperatures for relaxing. Maintaining comfortable temperatures requires constant adjustment, or may not be possible.
These temperature control problems are well known to HVAC suppliers, installers, and house occupants. Zone control systems have been developed to improve temperature control. Typically, a small number of thermostats are located in different areas of the house, and a small number of mechanized airflow dampers are placed in the air distribution ducts. A control unit dynamically controls the HVAC equipment and the airflow to simultaneously control the temperatures at each thermostat. These conventional systems are difficult to retrofit, and provide limited function and benefit. They are provided by several companies such as: Honeywell, 101 Columbia Road, Morristown, N.J. 07962; Carrier, One Carrier Place, Farmington, Conn. 06034; Jackson Systems, LLC100 E. Thompson Rd., Indianapolis, Ind. 46227; Arzel Zoning Technology, Inc., 4801 Commerce Parkway, Cleveland, Ohio 44128; Duro Dyne, 81 Spence Street, Bay Shore, N.Y. 11706; and EWC Controls, Inc., 385 Highway 33, Englishtown, N.J. 07726.
With only a few zones, there can still be significant temperature variations from room to room within a zone. A few systems have proposed thermostats for each room and airflow control devices for each air vent, but no practical solution for easy retrofit has been disclosed. As the number of independent zones increases, it becomes more complex to specify an appropriate setting for each zone while providing convenient centralized and remote control. Typical residential HVAC systems are designed to produce one fixed rate of heating and cooling, so adapting the existing systems to provide heating or cooling for only one or two rooms is difficult. These systems do provide methods to measure energy usage or provide information to help reduce energy use. They have not been widely adopted, because they are expensive, difficult and intrusive to install in most existing houses, and provide limited utility and benefit compared to their cost and inconvenience.
U.S. Pat. No. 5,348,078 issued Sep. 30, 1994 and U.S. Pat. No. 5,449,319 issued Sep. 12, 1995 to Dushane et. al describe a retrofit room-by-room zone control system for residential forced air HVAC systems that uses complex electrically activated airflow control devices at each air vent. The devices are mechanically complex, each with a radio receiver, servo motor, and multiple mechanical louvers. The devices are powered by batteries that are recharged by a generator powered by airflow through the air vent. Another embodiment is described that uses wires connected to a central control unit to control the airflow control devices, adding complexity to the installation process. The airflow control devices replace the existing air grills, so the installation is visible, and multiple sizes and shapes of airflow control devices are needed to accommodate the variety of air vents found in houses. The devices are expensive and have no shared mechanisms for control or activation to reduce the cost of the multiple devices required. The preferred embodiment uses household power wiring for communications between the thermostats and the central control, requiring visible wires from a power outlet to the thermostat. A cited advantage of the system is it does not have sensors inside the ducts, so the system cannot make control decisions based on plenum pressure or plenum temperature, therefore excessive noise and temperatures may occur for some settings of the airflow control devices. The thermostats and common controller have complex interfaces with limited functionality, making the system difficult to use.
U.S. Pat. No. 5,704,545 issued Jan. 6, 1998 to Sweitzer describes another zone system where the airflow control devices are louvers actuated by a local electromechanical mechanism. This invention requires modification to the air ducts and connecting wires from the airflow control devices to the common controlling device. This system is expensive and difficult to retrofit.
U.S. Pat. No. 4,545,524 issued Oct. 8, 1985, U.S. Pat. No. 4,600,144 issued Jul. 15, 1986, U.S. Pat. No. 4,742,956 issued May 10, 1988, and U.S. Pat. No. 5,170,986 issued Dec. 15, 1992 to Zelczer, et al. describe a variety of inflatable bladders used as airflow control devices in air ducts. All of these are adapted for mounting in a way that requires access to the air ducts for cutting holes and inserting devices into the duct, and for the controlling air tube to pass from the inside of the air duct to the outside of the duct for passage to the device that provides the air for the bladders. These airflow control devices do not provide a way for non-intrusive installation.
U.S. Pat. No. 4,522,116 issued Jun. 11, 1985, U.S. Pat. No. 4,662,269 issued May 5, 1987, U.S. Pat. No. 4,783,045 issued Nov. 8, 1988, and U.S. Pat. No. 5,016,856 issued May 21, 1991 to Tartaglino describe a series of inflatable bladders of different shapes and control methods. The disclosed control methods relate to the air pressure and vacuum used to inflated and deflate the bladders. The bladder shapes are novel but different from those used in the present invention.
U.S. Pat. No. 5,234,374 issued Aug. 10, 1993 to Hyzyk, et al. describes an inflatable bladder used as an airflow control device installed inside an air duct at an air vent. The bladder is inflated by a small blower also mounted in the air vent and powered by a battery. It receives control signals from a separate thermostat located in the room. This devices uses substantial power and battery life is limited. Since the blower for inflating the bladder is located at the air vent, noise from the blower is a problem which the inventor provides a muffler to help control. Each bladder is an independent unit and there is no sharing of components for controlling or powering, so there are no savings when many airflow devices are used in a zone control system. The device does provide a practical solution for providing centrally controllable airflow devices for each air vent in a house.
U.S. Pat. No. 5,772,501 issued Jun. 30, 1998 to Merry, et al. describes a system for selectively circulating unconditioned air for a predetermined time to provide fresh air. The system uses conventional airflow control devices installed in the air ducts and the system does not use temperature difference to control circulation. This system is difficult to retrofit and does not exploit selective circulation to equalize temperatures.
U.S. Pat. No. 5,024,265 issued Jun. 18, 1991 to Buchholz, et al. describes a zone control system with conventional thermostats located in each zone. This system teaches one method for distributing conditioned air to zones based dependent on the zone that has the greatest need for conditioning. However, the thermostats make on-off requests for conditioning based on local set points, so the system must deduce need based on the duty cycle of on-off requests. The control system does not have access to the actual temperature in the zone nor any other characteristic of the zone such as thermal resistance or thermal capacity. This system is not practically adaptable to a residential system.
U.S. Pat. No. 5,341,988 issued Aug. 30, 1994 to Rein, et al. describes a hierarchical wireless control system for zone control. This system is designed for large commercial buildings and is not practically adaptable for retrofit to a house.
U.S. Pat. No. 6,116,512 issued Sep. 12, 2000 to Dushane, et al. describes a wireless thermostat system where each wireless device has a number of programming functions for setting temperature and time schedules. Each thermostat function must be programmed at each device and there is no method to share programming effort or information between devices. The cost and complexity of a full functioning thermostat is duplicated for each device. The number of input buttons and the display capabilities at each device is limited, so programming is complex and functionality is limited.
U.S. Pat. No. 6,213,404 issued Apr. 10, 2001 to Dushane, et al. describes another wireless thermostat device comprising battery wireless thermometers reporting to a wireless thermostat. This device provides no method for entering commands at the wireless thermometer and uses a fixed slow rate of reporting the temperature stored at the wireless thermometer. The system is not adapted for use with a zone control system.
U.S. Pat. No. 5,224,648 issued Jul. 6, 1993 to Simon, et al. describes a wireless HVAC system using spread spectrum radio transmission technology. The control architecture requires reliable two-way communication and is not practical for battery powered operation. The described system cannot operate with infrequent and unreliable transmissions from the wireless thermometers and is not adaptable for low cost installation into existing residential HVAC systems.
U.S. Pat. No. 5,711,480 issued Jan. 27, 1998 to Zepke, et al. describes and claims using wireless SAW transmitters and receivers in an HVAC system. The patent teaches only the replacement of other wireless technology such as described in previously cited U.S. Pat. No. 5,224,648 with SAW based wireless technology and does not add to the art of retrofit zone climate control.
U.S. Pat. No. 5,782,296 issued Jul. 21, 1998 to Mehta describes a thermostat that has several 24-hour temperature schedules that are specified by entering a complex sequence of commands using a small number of buttons. The display can only display a small portion of the data of each temperature schedule at one time. Using this type of interface to program multiple temperature schedules for multiple zones would take great effort and is complex. This device is not practically adaptable for use in a room-by-room zone control system for a house.
U.S. Pat. No. 4,819,714 issued Apr. 11, 1989 to Otsuka, et al. describes a device for specifying multiple temperature schedules for multiple thermostats. It uses a display and a set of buttons designed specifically for this purpose. The system is designed for use with programmable thermostats that can be set locally or the device can program the thermostats with data entered at the central control. This device provides only a way of programming each thermostat with a common device, and is not adapted to controlling rooms within a house, a group of rooms, or the entire house, with a single temperature schedule. It provides no means for saving temperature schedules or grouping temperature schedules into temperature programs for the entire house. The device is not practical for adapting to a residential house.
U.S. Pat. No. 5,949,232 issued Sep. 7, 1999 to Parlante describes a method for measuring the relative energy used by each unit of many units served by a single furnace based on the accumulated time each unit draws energy. The method prorates the total based on time and does not account for different rates of energy use by each unit. The method requires individual timers for each unit and a method for communicating times to a central location. The method does not provide accurate results when each unit draws energy at different rates from the common source, and is not adaptable to a residential zone controlled forced air HVAC system.
U.S. Pat. No. 6,349,883 issued Feb. 26, 2002 to Simmons, et al. describes a control system for a set of zones that draw energy form a common supply. The system claims to save energy using occupant sensors and parameters entered locally in each zone to request conditioning only when the zone is occupied. The system does not have a centralized way to specify and control the zones as groups or as an entire house, and the system is not practical for residential retrofit or use.
U.S. Pat. No. 5,884,384 issued Mar. 23, 1999 to Griffloen describes a method for installing a tube inside another tube using a fluid under pressure. This method is not adaptable to air ducts because air duct are variable size, have irregular bends and corners, and are designed to withstand very small pressure differences.
The prior art individually or in combination does not provide a practical means for providing a zone control system or retrofit to existing HVAC residential buildings and homes. Individual components needed for each room have replicated components that could be shared to reduce cost. Installation of the components requires access and or modification to existing air ducts and changing or modifying objects visible to the occupant of the rooms. The control systems are complex and difficult to control, so the occupants are not able to get full benefit from zone control. The control systems provide no information about the energy used to condition each room nor predictions that help the occupants make informed decisions about comfort versus energy savings. Prior systems provide no means for diagnosing energy usage to identify HVAC equipment or building problems that can be cost-effectively repaired.